Electrical Head Scratcher

[JRC]

The critter is a 2013 Elevation 3612.
I went out to do the monthly maintenance run of my Onan 5500. I disconnected the shore power and tried to start it....nothing but a clank. I checked the voltage on the battery with a meter and it's 12.4 vdc.

I checked the slides and they are inoperative as are the 12v interior lights and fans. The landing gear is inoperative as well.

The battery switch is "on".

However, with shore power hooked up I can operate the slides, fans, and landing gear, as well as interior 12v lights.. But the Onan starter won't engage with shore power.

I also checked the chassis ground in the battery compartment and it's clean and tight. The unit is hooked up 24-7 in order to keep the battery charged.

I would appreciate any suggestions ya'll might have.

Thanks in advance.

[2slick]

I would suggest testing battery under load. Voltage may drop drastically under load. On shore power, converter is supplying 12 VDC.


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[BipeFlier]

Check the voltage at the Onan starter switch to the frame ground. This will tell you more than just battery voltage. If it is low, basic troubleshooting to find the bad connection.

[r2millers]

Yes, 12.4 shows a weak battery as a full charged one would show about 12.8 volts. Still a bit surprised you wouldn't get it to turn over, however, if lights don't work with such low draw, sounds like the battery is toast.

I'd expect the battery will solve your problem, however, I would also check the fuses in your converter to ensure you're getting voltage to the battery. You could also "jump" the existing batteries to start the generator and test the amps or voltage with a vom at the terminals. Again, there you should see about 13.8-14.2 volt with the generator running.

Keep in mind, when connected to shore power, you don't have direct current to start the generator. All is 12volt there and has to at least charge low batteries first before it will turnover.

One last piece, your main switch in the batt compartment that connects after 20-30 second of the generator running, will not operate without reasonable full voltage, and even if a low battery were to turn over the generator, it Will Not Start.

Yes, ask me how I know, after pulling the generator spark plug, carb, etc.

[DavisK]

Did you check the connections at the generator's starter to make sure they are clean and tight?

[JRC]

It turned out to be the battery. I guess I was fooled by the surface charge on the battery indicating above 12v and assuming everything should be okay. I checked the voltage at the distribution panel (no shore power) and it showed 12+ volts also.

I turned on the battery compartment light with the Volt meter hooked up and the voltage fell to around 8v with a dim bulb. Thanks to you all for your comments.

[TexSon]

Yep, a battery with a cell that just died will show 12+ volts until you put a load on it and then will drop to 8 or 9v. Make sure to get a deep cycle storage battery rather than just a starter (car) battery. They cost a bit more but usually last longer and you deep discharge them without damaging them unlike a starter battery.

[r2millers]

To tag on to Texson's comments,
From a website online...

"Deep cycle batteries are designed with thicker lead plates, which have less overall surface area than their thinner SLI counterpart. Because of the reduced availability of surface area for chemical reactions, deep cycle batteries produce less current than an SLI type battery, yet they produce that current for longer periods of time. Deep cycle batteries can be discharged up to 80 percent DOD without damage depending on the model. In order to increase battery life, manufacturers recommend discharging deep-cycle batteries only down to 50 percent in order to increase battery life."

SLI = Start/Lighting/Ignition
DOD= Depth of Discharge